KR100429921B1 - Low viscosity thermoplastic compositions for structures with enhanced moisture vapour permeability and the utilisation thereof in absorbent articles - Google Patents

Abstract

The present invention relates to a thermoplastic composition for producing a layer that is impermeable and moisture permeable by coating the composition on a substrate. This thermoplastic composition contains a suitable thermoplastic polymer and a suitable hydrophilic plasticizer that also enhances the moisture permeability of the film or layer made from the thermoplastic composition. Layers made from the thermoplastic compositions of the present invention can be used in a variety of applications where moisture permeability is desirable, such as in absorbent products such as diapers, sanitary napkins, panty liners and incontinence products, and also protective bedding covers, protective clothing, and the like.

Description

LOW VISCOSITY THERMOPLASTIC COMPOSITIONS FOR STRUCTURES WITH ENHANCED MOISTURE VAPOUR PERMEABILITY AND THE UTILISATION THEREOF IN ABSORBENT ARTICLES}

Thermoplastic films that provide moisture permeability and provide a liquid barrier are known in the art. Although it does not allow water vapor to flow through openings or holes in the material, it absorbs moisture on one side of the film with a higher vapor concentration and removes or evaporates it on the other side of the film with a lower vapor concentration, thereby allowing a significant amount of water vapor to pass through the film. Particular preference is given to hydrophilic continuous films which deliver.

WO 95/16746, for example, includes (a) block copolyether esters, block copolyether amides (for example Pebax ™) and / or polyurethanes, and (b) thermoplastic polymers incompatible with (a) and c). A film made from a mixture of compatibilizers is described. This film is impermeable and the moisture vapor permeability of this film is about 700 g / m 2 · day. US 5,447,783 also describes a multi-component film structure that is vapor permeable, waterproof, and has three or more layers. The outer layer is a hydrophobic copolyetherester elastomer with a thickness of 1.3-7.6 μm and a WVTR of 400-2500 g / m 2 · 24 hours, the inner layer is 7.6-152 μm thick and a 3500 g / m 2 · 24 hour WVTR It is the above hydrophilic copolyether ester elastomer.

US 5,445,875 describes breathable laminates that are waterproof, bleeding and virusproof. This laminate contains woven / non-woven fabrics and extruded films such as Hytrel ™ having a thickness of about 1 mil (25.4 μm).

Other composite laminates are described, for example, in US Pat. No. 5,599,610, which describes a three-layer fabric for surgical gowns comprising an outer layer of woven fabric and an inner layer of microporous polyurethane membrane. The thickness of the microporous film is 12-55 μm, the MVTR is 1100 g / m 2 · 24 hours when upright and 5500 g / m 2 · 24 hours when upside down (ASTM E96-B). The layers are connected using a polyether-polyurethane adhesive.

Similarly, US 5,532,053 describes highly breathable medical films that can be laminated onto nonwoven materials. This laminated film contains the first layer of the polyetherester copolymer and the second and third layers selected from the specific group of polymers. The MVTR of this film is greater than 750 g / m 2 · 24 hours (ASTM F1249) and the thickness is less than 1 mil (25.4 μm), preferably 0.6 mil to 0.75 mil (15-19 μm).

US 4,938,752 describes absorbent articles containing a film of copolyetherester having a reduced water permeability, a water vapor permeability of 500 g / m 2 · 24 hours (measured in a particular described test) and a thickness of 535 μm. have. There is no disclosure of a supporting substrate.

US 4,493,870 describes a flexible laminated waterproofing product comprising a textile material covered with a copolyetherester film having an MVTR of at least 1000 g / m 2 · 24 hours (ASTM E96-66) and a thickness of 5 to 35 μm. .

GB 2024100 has a breathable but liquid-resistant microporous hydrophobic outer layer, and a flexible laminated water resistant layer containing a hydrophilic inner layer of polyetherpolyurethane with an MVTR greater than 1000 g / m 2 · 24 hours. The article is described.

The applicant's application (PG, case CM1800F), entitled “Low Viscosity Thermoplastic Compositions for Moisture-Proof Structures and Absorbent Products,” filed on the same date as the present application, has desirable features of moisture permeability and impermeability. Thermoplastic compositions for making moisture-permeable, impermeable, hydrophilic continuous layers are described. Thermoplastic compositions are preferred thermoplastic polymers such as polyurethanes, poly-ether-amide block copolymers, polyethylene-acrylic acid copolymers, polyethylene oxides and copolymers thereof, polylactides and copolymers, polyamides, polyester block copolymers, Sulfonated polyesters, poly-ether-ester block copolymers, poly-ether-ester-amide block copolymers, polyacrylates, polyacrylic acids and derivatives, ionomers, polyethylene-vinyl acetates having a vinyl acetate content of more than 28%, Polyvinyl alcohol and copolymers thereof, polyvinyl ethers and copolymers thereof, poly-2-ethyl-oxazolines and derivatives, polyvinyl pyrrolidone and copolymers thereof, thermoplastic cellulose derivatives, or mixtures thereof. In addition, the preferred thermoplastic compositions described can be readily processed to provide a coating with a desired thickness on a substrate, thus avoiding the need for complicated traditional extrusion tools. This can be done by changing the viscosity of the thermoplastic polymer by incorporating an appropriate plasticizer to lower the viscosity in the thermoplastic composition. This makes it possible to utilize the typical processing conditions known in the art using the above preferred compositions to coat the low viscosity hot melt directly on the substrate to form a moisture-permeable, impermeable film or layer.

Surprisingly, by appropriately selecting a plasticizer or a mixture of plasticizers, a moisture-permeable, moisture-permeable, water-impermeable film or layer, compared to a corresponding film or layer prepared from a composition that does not contain a plasticizer or a mixture of plasticizers, is produced. It has been found that thermoplastic compositions for preparation can be obtained. Preferred plasticizers or mixtures of plasticizers, of course, can adjust the viscosity of the thermoplastic composition, such that a film or layer is made from the thermoplastic composition by a simplified coating process.

Summary of the Invention

The present invention relates to a thermoplastic composition for producing a moisture-permeable impermeable layer by coating the composition on a substrate. Such compositions contain the following:

Polyurethanes, poly-ether-amide block copolymers, polyethylene-acrylic acid copolymers, polyethylene oxides and copolymers thereof, polylactides and copolymers, polyamides, polyester block copolymers, sulfonated polyesters, poly-ethers -Ester block copolymers, poly-ether-ester-amide block copolymers, polyacrylates, polyacrylic acids and derivatives, ionomers, polyethylene-vinyl acetates, polyvinyl alcohols and copolymers thereof having a vinyl acetate content of more than 28% by weight , Polyvinyl ethers and copolymers thereof, poly-2-ethyl-oxazolines and derivatives, polyvinyl pyrrolidone and copolymers thereof, thermoplastic cellulose derivatives, or mixtures thereof Mixture of

Suitable compatible hydrophilic plasticizers or mixtures of hydrophilic plasticizers;

The viscosity of the thermoplastic composition is 50 to 4000 Poise at a frequency of 1 rad / s and a temperature of 210 ° C. or less, less than 2000 Poise at a frequency of 1000 rad / s and a temperature of 210 ° C. or less,

The hydrophilic plasticizer is selected from the group consisting of acids, esters, amides, alcohols, polyalcohols or mixtures thereof.

The present invention relates to a thermoplastic composition for producing a moisture vapor permeable liquid impermeable layer by coating the composition on a substrate. The compositions of the present invention can be used in a variety of applications where moisture permeability is desired, such as in absorbent products such as diapers, sanitary napkins, pantyliners and incontinence products, protective bedding covers, protective clothing, and the like.

Suitable thermoplastic polymers for inclusion in the compositions according to the invention include polyurethanes, poly-ether-amide block copolymers, polyethylene-acrylic acid copolymers, polyethylene oxides and copolymers thereof, polylactides and copolymers, polyamides, Polyester block copolymers, sulfonated polyesters, poly-ether-ester block copolymers, poly-ether-ester-amide block copolymers, polyacrylates, polyacrylic acids and derivatives, ionomers, vinyl acetate content Excess polyethylene-vinyl acetate, polyvinyl alcohol and copolymers thereof, polyvinyl ethers and copolymers thereof, poly-2-ethyl-oxazolines and derivatives, polyvinyl pyrrolidone and copolymers thereof, thermoplastic cellulose derivatives, or Mixtures thereof.

Thermoplastic poly-ether-amide block copolymers (eg Pebax ™), thermoplastic poly-ether-ester-amide block copolymers, thermoplastic polyester block copolymers (eg Hytre ™), thermoplastic polyurethanes (eg Estane ™), or mixtures thereof, are particularly preferred thermoplastic polymers.

Such thermoplastic polymers or mixtures of polymers may typically be very viscous in the molten state at processing conditions typical for known processing of film or layer formation, for example extrusion processing involving a powerful screw extruder. For example, their viscosity may be 20 ° C. higher than the Differential Scanning Calorimetry (DSC) melting point (in the case of a mixture of polymers showing a DSC peak or more than one peak, which is the temperature found to correspond to the highest DSC peak) and Typically at a frequency of 1 rad / sec exceeds 5000 Poise.

The viscosity of the thermoplastic composition of the present invention can be preferably adjusted by containing in the thermoplastic composition a suitable plasticizer, or a mixture of plasticizers, which is compatible with the thermoplastic polymer and lowers the viscosity of the thermoplastic polymer or mixture of polymers in the molten state.

Thermoplastic compositions of the invention containing preferred hydrophilic plasticizers or mixtures of hydrophilic plasticizers have the following composite viscosity (η *):

50 Poise <η * <4000 Poise, preferably 100 Poise <η * <2000 Poise, more preferably 100 Poise <η ＊ <1000 Poise and 1000 rad / at a frequency of 1 rad / s and at temperatures up to 210 ° C. η * <2000 Poise, preferably η * <1000 Poise, more preferably η * <500 Poise [η *] represents the composite viscosity of the thermoplastic polymeric composition at a frequency of s and a processing temperature (T) of 210 or less. ]. Preferably the temperature T is 200 ° C. or less, more preferably 180 ° C. or less, most preferably 200 ° C. to 50 ° C.

The thermoplastic compositions having the complex viscosities mentioned will not only coat the coating onto the substrate with the required thickness of the low viscosity hot melt composition, while maintaining the advantageous properties of the thermoplastic polymers desirable for providing a hydrophilic continuous moisture permeable, impermeable layer or film. Devices known in the art and typically coating conditions are used to allow the film or layer to be coated onto a substrate.

Thermoplastic compositions having such a viscosity can also provide very thin films or layers.

By selecting the hydrophilic plasticizer contained in the thermoplastic composition from acids, esters, amides, alcohols, polyalcohols or mixtures thereof, compared to the corresponding layer or film formed from the thermoplastic composition containing the same thermoplastic polymer but no plasticizer It was unexpectedly found that the enhanced moisture permeability characteristics of the resulting layers or films formed from such thermoplastic compositions were obtained.

Preferred hydrophilic plasticizers or mixtures of hydrophilic plasticizers can also adjust the viscosity of the thermoplastic composition to a desired value in order to be processed by coating the thermoplastic composition on a substrate with a layer or film having a desired thickness.

Preferred plasticizers according to the invention are citric acid esters, tartaric acid esters, glycerol and esters thereof, sorbitol, glycolate, and mixtures thereof.

Preferably the thermoplastic composition of the invention comprises 10 to 80%, more preferably 25 to 70% of the thermoplastic polymer or mixture of polymers and 20 to 90%, preferably 30 to 75% of the weight of the thermoplastic composition Suitable plasticizers or mixtures of plasticizers.

In addition, the thermoplastic composition of the present invention may be further added to further improve the processability and mechanical properties of the composition as well as other features of the films or layers formed from such thermoplastic compositions such as adhesion, resistance to aging by light and oxygen, appearance, and the like. It may contain a component of.

Such optional components include tackifying resins or mixtures of tackifying resins having a softening point of 125 ° C. or less. Preferred resins that may be present up to 50% by weight of the thermoplastic composition include rosin and rosin esters, hydrocarbon resins, aliphatic resins, terpene and terpene-phenolic resins, aromatic resins, synthetic C ₅ resins, mixtures of synthetic C ₅ -C ₉ resins, and Mixtures thereof. Other optional components of the thermoplastic composition include antioxidants, anti-ultraviolet agents, pigments, and mixtures thereof, which may be present in the composition at levels up to 10% of the composition weight.

The thermoplastic composition according to the invention provides a thermoplastic polymer or a mixture of polymers and a suitable plasticizer or a mixture of plasticizers, and the components are heated in a molten state with the desired composite viscosity η * by heating the components and mixing them with, for example, a suitable mixer known in the art. It can be prepared by a process typically comprising the steps of forming a thermoplastic composition of the.

According to the invention, the moisture-permeable, impermeable layer can be formed from the composition by coating the thermoplastic composition of the invention on a substrate. The water vapor transmission rate of the film or layer formed from the thermoplastic composition of the present invention is 100 g / m 2 · 24 hours or more, preferably 300 g / m 2 · 24 hours or more, most preferably 500 g / m 2 · 24 hours or more and the thickness is 0.5 It is more than micrometer.

The method for producing a layer or film from the thermoplastic composition according to the invention typically provides steps for providing the composition, heating it to make it fluid, and coating the composition in molten state onto a substrate with a layer having a desired viscosity. Include. The substrate may simply be a constituent substrate such that the thermoplastic composition is coated on the substrate to form a film or layer of desired thickness and subsequently separated from the substrate and used as is, in one embodiment of the invention a thermoplastic composition and A moisture-permeable and impermeable composite can also be formed, in which the composition contains a coated substrate, wherein the substrate is also preferably moisture-permeable.

Such an embodiment of the present invention provides a moisture-permeable and water-impermeable composite, in which the contribution to the composite material of the layer formed from the thermoplastic composition of the present invention is attributed only to the provision of a liquid barrier, and thus can be advantageously provided as thinly as possible. The remaining performance physical features are preferably provided by the provided substrates, which therefore preferably also act as a support layer.

The substrate or support layer is preferably also water vapor permeable and the water vapor transmission rate is preferably 1000 g / m 2 · 24 hours or more, more preferably 300 g / m 2 · 24 hours or more, most preferably 500 g / m 2 · 24 hours or more It may be any useful layer.

Suitable substrates for use as support layers in the present invention include two-dimensional planar micro and macroporous films; Macroscopically expanded film; Formed perforated film; Nonwoven and woven layers are included. According to the invention, the holes in the layer can be of any shape, but are preferably spherical or elliptical and can also be changed in size. The pores are preferably evenly distributed over the entire surface of the layer, but a layer is also implemented in which the pores are only in specific surface areas.

A suitable two-dimensional porous planar layer on the back can be made of any material known in the art, but is preferably made from commonly available polymeric materials. Suitable materials are, for example, Goretex ™ or Sympatex ™ type materials well known in the art for use in so-called breathable garments. Other suitable materials include Minnesota Mining and Manufacturing Company, St. Paul, Minnesota, USA] XMP-1001 and Exxaire XBF-101W supplied by Exxon Chemical Company. As used herein, the term two-dimensional planar layer refers to layers having a depth of less than 1 mm, preferably less than 0.5 mm, wherein the holes have an average uniform diameter with their length and do not protrude from the plane of the layer. Perforated materials for use as backs in the present invention may be prepared according to any method known in the art such as those described in EPO 293 482 and references therein. The size of the holes made by this method can also be increased by applying force to the plane of the backing layer (ie stretching the layer).

Films formed with appropriate holes include films with discrete holes that extend beyond the horizontal plane of coating facing the surface of the layer towards the center to form protrusions. The protuberance has an orifice located at the terminal end. Preferably the protrusions are funnel shaped and similar to those described in US 3,929,135. The hole located in the plane and the orifice itself located at the terminal end of the protrusion may be one circular or non-circular where the cross section of the orifice at the end of the protrusion is smaller than the cross section of the hole located in the sheath facing the surface of the layer. Preferably the film formed such that the aperture is substantially unidirectional to have fluid transport towards one or more, if not one, directional central portions.

Macroscopically expanded films suitable for use in the present invention include, for example, the films described in US 4,637,819 and US 4,591523.

Preferred support layers for use in the present invention include woven and nonwoven layers, most preferably layers of hydrophobic fibers such as hydrophobic nonwovens.

The composite of this preferred embodiment of the present invention is particularly advantageous as it enables the thermoplastic composition to provide a composite which can be coated as a layer of desired thickness on a supporting substrate. Apparatuses and typical coating conditions known in the art for direct coating of low viscosity hot melt can be readily used to provide the thermoplastic composition with the desired thickness.

A possible method for forming a composite laminate by coating a thermoplastic composition on a substrate that acts as a support layer is described in PCT application WO 96/25902.

At least at the coating temperature, the thermoplastic composition in layer form exhibits adhesion on the supporting substrate to form the desired composite such that no additional adhesive is required for permanent attachment between the thermoplastic composition and the substrate. In some applications, it may also be desirable for the thermoplastic composition to be formulated to be tacky at any temperature, ie to have the typical properties of a pressure sensitive adhesive.

The thermoplastic compositions of the present invention and the moisture-permeable, impermeable layers and composites formed therefrom can be used in many applications where impermeable and moisture-permeable are desirable. In particular the invention provides absorbent articles such as diapers, sanitary napkins, panty liners and incontinence products; Sweating pads such as armpit-, wrist- and head sweating pads, feather inserts, shoe inserts, hat bands and chest pads; It can be effectively used in protective bedding cover, protective clothing and the like. Preferably the water vapor transmission rate of the moisture-permeable and impermeable layer and composite formed from the thermoplastic composition of the present invention is 100 g / m 2 · 24 hours or more, more preferably 300 g / m 2 · 24 hours or more, most preferably 500 g / M 2 · 24 hours or more.

The moisture-permeable, impermeable composite structure formed by coating the thermoplastic composition of the present invention on a suitable substrate can be used in particular as a back for absorbent articles, in particular sanitary napkins and pantyliners. Such articles typically contain components known to those skilled in the art such as liquid permeable tops, absorbent centers and backs and may optionally contain fastening means, wings, and the like.

Preferred hydrophilic plasticizers of the present invention are also inherently moisture-permeable thermoplastic polymers, such as polyolefins such as polyethylene or polypropylene, or substantially thermoplastic, impermeable, styrenic block copolymers that are added to the final thermoplastic that is moisture-permeable. The composition can be provided.

According to the invention Rheometrics Co. Composite viscosity is measured using the Rheometer RDA-II sold by the company. Moisture permeability is measured as water vapor transmission rate (WVTR) at 23 ° C. according to ASTM E-96 “Upright Cup” method.

Claims (12)

It contains the following polymers and plasticizers, and has a viscosity of 50 to 4000 Poise at a frequency of 1 rad / s and a temperature of 210 ° C. or less and less than 2000 Poise at a frequency of 1000 rad / s and a temperature of 210 ° C. or less. A thermoplastic composition for producing a moisture-permeable impermeable layer that has been strengthened by coating on a substrate: Polyurethanes, poly-ether-amide block copolymers, polyethylene-acrylic acid copolymers, polyethylene oxides and copolymers thereof, polylactides and copolymers, polyamides, polyester block copolymers, sulfonated polyesters, poly- Ether-ester block copolymers, poly-ether-ester-amide block copolymers, polyacrylates, polyacrylic acids and derivatives, ionomers, polyethylene-vinyl acetates having a vinyl acetate content of more than 28% by weight, polyvinyl alcohols and air thereof Thermoplastic polymers selected from the group consisting of copolymers, polyvinyl ethers and copolymers thereof, poly-2-ethyl-oxazolines and derivatives, polyvinyl pyrrolidone and copolymers thereof, thermoplastic cellulose derivatives, and mixtures thereof Mixtures of polymers, and Suitable compatible hydrophilic plasticizers or mixtures of hydrophilic plasticizers selected from the group consisting of acids, esters, amides, alcohols, polyalcohols or mixtures thereof. The method according to claim 1, wherein 10 to 80% by weight of the polymer or mixture of polymers of the thermoplastic composition, 20 to 90% by weight of the plasticizer or mixture of plasticizers, 0 to 50% by weight of a suitable compatible adhesive A thermoplastic composition comprising a topical resin. The method of claim 1 or 2, wherein the thermoplastic polymer or mixture of polymers is selected from thermoplastic poly-ether-amide block copolymers, thermoplastic poly-ether-ester-amide block copolymers, thermoplastic polyester block copolymers, thermoplastic polyurethanes. Or a mixture thereof. 3. The thermoplastic composition of claim 1, wherein the hydrophilic plasticizer is selected from citric acid esters, tartaric acid esters, glycerol and esters thereof, sorbitol, glycolate, and mixtures thereof. 3. A mixture according to claim 1 or 2, wherein the tackifier resin is a mixture of rosin and rosin esters, hydrocarbon resins, aliphatic resins, terpenes and terpene-phenol resins, aromatic resins, synthetic C ₅ resins, synthetic C ₅ -C ₉ resins. And mixtures thereof. A moisture-permeable layer formed by coating the thermoplastic composition of claim 1 on a substrate, which is impermeable, has a water vapor transmission rate (WVTR) of at least 300 g / m 2 · 24 hours and a thickness of at least 0.5 μm. A breathable and impermeable composite, wherein the layer of claim 6 is coated onto a breathable substrate. Absorbent article comprising the moisture-permeable and impermeable layer or composite according to claim 6. Providing a thermoplastic polymer or a mixture of polymers, Providing a suitable compatible hydrophilic plasticizer or mixture of hydrophilic plasticizers, and -Heating said thermoplastic polymer or mixture of polymers and said plasticizer or mixture of plasticizers and mixing them to form a molten thermoplastic composition. Providing a thermoplastic composition, Heating the thermoplastic composition to make it flowable, and -Coating said thermoplastic composition on a substrate with a layer of desired thickness, the method of producing a layer from the thermoplastic composition of claim 1. The thermoplastic composition of claim 2 containing from 25 to 70% by weight of the polymer or mixture of polymers. The thermoplastic composition of claim 2 containing 30 to 75% by weight of a plasticizer or a mixture of plasticizers.